Writing unit locking mechanism in a multiple-point writing implement including a mechanical pencil unit

A multiple-point writing implement comprising, in combination:

• a holder cylinder having a forward aperture and a rear end;
• a mechanical pencil unit with a writing end movably positioned in said holder cylinder for movement between a normal retracted position and an advanced writing position wherein said writing end projects out of said forward aperture of the holder cylinder, said pencil unil having a unit cylinder and a chuck disposed in the unit cylinder for normally chucking a writing lead;
• means for making said chuck inoperative for releasing the lead from the chuck to feed it out of the unit cylinder, said means having tail means fixedly connected to said chuck within said unit cylinder and operable to make the chuck inoperative only when it is pushed toward said writing end of the pencil unit while the pencil unit is held stationary in said writing position;
• a catch shoulder provided on said unit cylinder of the pencil unit:
• at least one other writing unit with a writing end, provided in said holder cylinder in substantially parallel relationship with said pencil unit and movable between a normal retracted position and an advanced writing position wherein the writing end thereof projects out of said aperture of the holder cylinder;
• writing unit selection means provided at said rear end of the holder cylinder and movably mounted for movement out of the holder cylinder and having a writing unit push member movable within the holder cylinder between positions in which it is opposed to the respective units, said writing unit push member being engagable with a selected unit for pushing the selected unit to the writing position thereof when the writing unit selection means is moved into the holder cylinder;
• catch means on said writing unit selection means;
• first engagement means in a position for engaging said catch means to arrest and hold the writing unit selection means near the position of the selection means to which the selection means has been pushed to shift the selected unit to the writing position thereof;
• second engagement means in a position for engaging said catch shoulder on said pencil unit when said pencil unit is in the writing position to arrest and hold the pencil unit in that position;
• and
• manually operable means operably associated with said first and second engagement means outside the holder cylinder for simultaneously disengaging the first and second engagement means and the catch means and catch shoulder, respectively, when the manually operated means is operated, thereby to allow the selected unit to return to its retracted position.